In modern electric drives, monitoring of the winding temperature on the stator unit is generally provided for safety reasons. In this manner, subsequent electronics or, if needed, an emergency shutdown, can be initiated in the event of overheating. The particular temperature data detected by a temperature sensor situated in the stator unit is often transmitted via a position measuring device, a rotary encoder, for example, which is situated on the drive. The position measuring device transmits to the sequential electronics not only the detected position data for further processing, but also the temperature data and possibly other data. Reference may be made to Japanese Published Patent Application No. 8-261792 in this regard. In particular in the case of serial data transmission for sequential electronics, the particular temperature is determined directly from the output signals sent by the temperature sensor in a signal processing unit of the position measuring device or in the sensor electronics. However, because of the normally high motor currents in the region of the stator unit, significant interference effects on the signal processing unit or sensor electronics result. Since the signal processing unit is also used for further processing of position-dependent signals, such interference also adversely affects the processing of the position data in the position measuring device. Such interference effects can be minimized only using a relatively high expenditure of resources, for example, by suitable interference suppression measures.
It is an aspect of the present invention to provide a system for monitoring the temperature in the stator unit of an electric drive which may ensure accurate temperature determination with the smallest possible expenditure of resources. The least possible interference of other sensor systems on the drive may result, in particular, of a position measuring device situated on the drive.